Since last month's cease-fire went into effect, shelling around the Ukrainian port city of Mariupol has decreased, but it is thought pro-Russian separatists remain poised to attack. For the city’s authorities, a major challenge is gaining the trust of residents, while at the same time rooting out informants who are passing sensitive information to the rebels.

Children still play in the squares of central Mariupol, but this city is holding its breath. With the constant threat of separatist invasion, city authorities here acknowledge the population remains deeply divided.

They estimate just 30 percent support the government while another 30 percent support the rebels. They say the remaining 40 percent are undecided, longing only for a return to normality.

For Mariupol’s Civil Defense Organization, this disunity makes the city even harder to secure. Ukrainian security services monitor mobile phone traffic to stop people from passing information to separatists. And there has been a spate of arrests in recent weeks as Ukrainian authorities try to root out suspected spies.

“All of these people were taking part in terrorist groups, and the relatives have no idea. What they have done? They transfer information, smuggle weapons, but mostly it’s sending information,” said Roman Sokolov, chairman of Mariupol Civil Defense Organization.

But this family disputes the official version of events. On Friday, Anna got a terrified phone call from her 14-year-old sister. She said armed men with no official identification papers had pushed their way into the house and beaten their father.

“My sister ran in here. She could see our father’s face had a bruise from this tool. His face had been beaten, and it looked like they’d beaten his head on the table," said Anna.

Anna said her father was not involved in politics, but the men took him away after beating him. She tried to follow them but she says they threatened to shoot her. Now she has no idea where he is.

“A person in our country is unprotected now; wherever he goes, he doesn’t have any rights. At this moment the political situation in Mariupol is like if you criticize the local administration, you are a separatist,” said Anna.

Perhaps nowhere is Mariupol’s atmosphere of mistrust more evident than in the suburb of Vastochniy. When a rocket attack in January killed 30 people here, Human Rights Watch investigators said it was highly likely that the rebels were to blame.

But in spite of the evidence, many continue to believe that the government was responsible, though they are too afraid to say so openly.

“The shelling of Vastochniy district, the shelling in Donetsk, when they hit the trolley bus, the shelling in Volnovaha when they hit the bus, 75 percent of the people here are sure that this was a provocation by the Ukrainian government,” said a man using the name Pasha.

Authorities in the region are facing a classic counterinsurgency dilemma: how to enforce security without losing the hearts and minds of local people. And as the war continues to send the local economy deeper into the abyss, it seems the government's position here may only get more precarious.